The partially cured fiberglass product of the present invention is capable of being used in its as-manufactured condition or as a shaped component of a subsequently manufactured product. Typically, the uncured fiberglass product is later cured in a heated press to form a shaped or board-like product. To appreciate the advance in the art provided by the present invention, the conventional rotary spinner fiberglass process will be described as a reference.
In broad outline, a fiberglass pack is formed from molten glass which is dropped onto a rotating spinner disc and the glass thereafter formed into small diameter streams of molten glass as it leaves the spinner disc through fine holes formed in the disc walls under the influence of centrifugal force. The streams of glass are then attenuated into fibers by a blast of hot gases which direct the fiber veil downward toward a takeaway conveyor. A binder, usually a thermosetting resin, is sprayed onto the falling veil of fibers so that a pack of fibers with binder applied thereto forms on the conveyor. The pack with binder applied thereto must be later heated in a curing press by a customer or purchaser of the product. The binder, upon fully curing, will bind the fibers one to the other to form a fully self-sustaining article which is usually a flat or shaped, board-like product.
Vaporization of the binder at the forming station is a significant problem because state and federal environmental regulations generally prohibit the release of vaporized binder into the atmosphere. To alleviate this problem, manufacturers spray water or another cooling fluid on the hot fiber veil at the forming station to cool the hot fibers before the application of binder. However, the fibers are still hot even after the application of water and therefore the application of binder to the hot fiber veil results in the vaporization of binder resulting in undesirable fumes. Further, the water and some of the binder, is removed from the pack on the air pervious takeaway conveyor located in the forming station. The undesirable fumes resulting from the vaporization of binder at the forming station require expensive pollution control equipment to remove the binder from the forming station gases prior to discharge of forming station gases to the atmosphere.
Binder application in the forming station in a desired amount of about 18% by weight of the fiberglass is typical of this process.
The instant invention differs from the above described conventional process and substantially alleviates the environmental concerns associated with vaporized binder in that a first amount of binder in an amount that approximates only about 1/7th of or substantially less than the desired amount of binder applied in a conventional process is applied at the forming station. Thereafter, in contrast to the conventional process described above, the pack is cured in an oven or a curing station so that a self-sustaining blanket is formed upon emerging from the curing station. The resulting low binder blanket is a feed blanket to which supplemental binder is later added. As a result, far lower quantities of binder and water are removed at the forming stations when making the low binder blanket and similarly small quantities of binder are removed at the curing station so that the treatment of the excess binder and other waste is greatly simplified. Further, it is believed that the process of the present invention can be carried out at a higher efficiency than the prior art process discussed above.
Additional supplemental or "second" binder which is needed to form a useful self-sustaining final product is added to the blanket after the "first" or preliminary application of binder has been made at the forming station and after the pack has been cured to form a blanket. Since the amount of the second or make-up binder cannot be added with great precision under production line conditions, an excess of the second binder is added at an impregnation or re-resination station. However, applying excess second binder to the cool blanket does not create pollution problems because the excess second binder can be removed or stripped by application of vacuum or a pressure drop to the moving blanket at a stripper station. The excess second binder that is removed may also be recycled.
It is preferred that the second binder be in a liquid form and substantially foam-free so as to enhance the ability of the stripper to remove excess amounts of second binder from the moving blanket. The use of a plurality of strippers enables the final binder content to be controlled to a desired level. Since the second binder is preferably applied at room temperature, the effluent handling problem is greatly simplified over the effluent handling conditions which exist at the conventional forming station. By the same token, since the stripper action removes only excess second binder applied at the re-resination station, the excess second binder can be applied and thereafter removed at room temperature and can be conveniently recycled. With proper configuration, a closed system can be utilized which eliminates nearly all atmospheric discharge and hence avoids or greatly reduces pollution concerns.
Depending on such cost factors as the cost of the additional, non-conventional equipment required and the throughput of a given line, all of the above may be accomplished at lower cost per unit of product produced than is experienced with current conventional techniques used to produce the same or functionally equivalent products.